Quick detachable, shielded electrical connector



R. LAY ETAL Aug. 21, 1962 QUICK DETACHABLE, SHIELDED ELECTRICAL.v CONNECTOR Filed Jan. 11. 1961 United States Patent Oiice 3,050,658 Patented Aug. 21, 1962 3,050,658 QUICK DETACHABLE, SHIELDED ELECTRICAL CONNECTOR Robert Lay, Frank B. Paul, and Gerald E. Roy, Flint,

Mich., assignors to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed Jan. 11, 1961, Ser. No. 81,991 2 Claims. (Cl. 315-85) This invention pertains to quick detachable electrical connectors, and particularly .to a shielded, readily detachable spark plug connector.

Heretofore, quick-disconnect spark plug connectors of the bayonet type have been ldevised wherein one part of the connector is Iformed with bayonet slots and the mating part is formed with projecting pins whereby the spark plug lead can be readily connected to and disconnected from the center electrode of the -spark plug by simultaneous axial and angular movement between the connecting parts. While it is possible to waterproof a quickdisconnect assembly of Ithe aforesaid type, due to the presence of the slots in one of :the connector parts optimum electrical shielding canno-t be readily achieved. The present invention relates to a quick-disconnect electrical connector, designed primarily for use in electrically shielded ignition systems, which provides both adequate waterproofing and electrical shielding. Moreover, these results are achieved fwith no increase in the number of parts or cost of manu-facture.

Accordingly, `among our objects are the provision of a waterproof and electrically shielded quick detachable electrical connector; the further provision of a quick-disconnect spark plug lead of the 'bayonet type which is both Waterproof and electrically shielded; and the still further provision of a readily attachable and detachable electrical connector comprising telescopic mating parts having coengaging lugs and grooves.

The aforementioned and other objects are accomplished inthe present invention by forming one or more external bayonet type grooves in one part `and one or more internally projecting lugs in the other part of the connector. Specilically, when the improved readily attachable and detachable connector is used as a spark plug lead, the shielding barrel of the spark plug is preferably formed with la pai-r of external bayonet type grooves adapted to receive and interlock with internal lugs `formed on a skirted nut supported by the end of a spark plug cable. The connector embodies spring means for biasing the nut against the shielding barrel as well as spring means for biasing a lead-through sleeve against the upper end of the spark plu-g insulator. In accordance with conventional practice the electrical connection between the spark plug lead and the center electrode is obtained through a spring, one end of which is carried by a ceramic sleeve that telescopically receives an end of Ithe spark plug cable.

These and further objects and advantages will be apparent from the ,following description, reference being had to the accompanying `drawing wherein a preferred embodiment of the present invention is clearly shown.

In the drawing:

FIGURE 1 is 'a cross sectional view of a shielded spark plug attached to its lead by the connector of -this invention;

FIGURE 2 is a perspective view of the connector parts in their disassembled condition.

With reference to FIGURE l, the connector of this invention is shown in conjunction with a shielded spark plug comprising an elongated tubular ceramic insulator 1t) carrying a center electrode assembly 12 and a tubular metal shell 14 carrying a ground electrode 16. A metal shielding barrel 18 is secured to the shell 14 and is coaxial with the upper end of the insulator 10. The insulator 10 is formed with shoulders, as shown, upon which upper and lower sealing gaskets 20 and `22 are seated to form a gas-tight joint between the insulator and the shell and shielding barrel assembly.

The center electrode `assembly 12 includes a metal contact plug 24 which is partially embedded in a conductive glass seal 26, `and a firing tip 28, the upper end of which is likewise partially embedded inthe glass seal. The lower end of Ithe firing tip 28 projects from the insulator 10 in spaced relation to the ground electrode 16 so as to `form a spark gap therewith.

The upper end of the tubular insulator it) receives the end of a shielded ignition cable 30 which terminates in an insulator sleeve 32 carrying a metal contact 34. Gne end of a spring 36 is 4suitably attached to the metal contact 34, and the other end of the spring 36 engages the contact 24 of the center electrode -assembly to establish electrical connection between the center electrode assembly and the ignition cable, or spark plug lead.

In accordance ywith the present inven-tion, la waterproof and shielded quick-disconnect is utilized to secure the terminal end of the ignition cable to 4the shielding barrel of the spark plug. Accordingly, the upper end of the shielding barrel 18 is lformed with a thin walled section having a pair of diametrically located external bayonet grooves 38 as clearly shown in FIGURE 2. Each groove 38 has a substantially axial entrance portion 38a, a circumferentially extending helical portion 38b and a locking portion 38C. The other part of the connector comprises a skirted nut 40 with a thin `walled section having a pair of diametrically loca-ted indent-ations, or internal lugs, 42, spaced inwardly Afrom the lower end thereof as clearly shown in FIGURE 2. The nut 40 receives a shielding sleeve 44 which has a ferrule 46 suitably attached to its inner end. A coil spring 48 is coniined between the ferrule 46 and the flanged end of the nut 40, as clearly seen in FIGURE 1. A sleeve 50 of insulating material is coaxially disposed within the met-al sleeve 44 and constitutes a guide for receiving the terminal end of the ignition cable 3i). The insulative sleeve Sil is yformed with an integral enlargement, or shoulder, 52 adjacent its lower end which is designed to abut and firmly engage the upper end of the tubular insulator 10. A second ferrule 54 engages the upper surface of the shoulder 52 on the insulator sleeve 5t?, and a second coil spring 56 is interposed between the `ferrules 46 and 54.

With the parts disconnected as shown in FIGURE 2, it is readily apparent that the connector enables ready attachment and detachment of the terminal end of the igni- -tion cable with the center electrode of the spark plug. To establish the connection, it is only necessary .to engage the lugs 42 on the nut 40 with the entrance portions 38a of the bayonet slots 38 on the upper end of the shielding barrel 18 and thereafter simultaneously exert axial pressure and eilect relative rotation between the nut 4i) and the shielding barrel 18 so as to connect the two parts. In so doing, an electrical connection is established by the spring 36 with the center electrode 12 of the spark plug, the spring 56 maintains the shoulder 52 of the insulative sleeve 50 in snug engagement with the upper end of the insulator 10 while the spring 48 maintains the lugs 42 interlocked fwith the 'bayonet grooves 38. To disconnect the spark plug lead from the spark plug, it is only necessary to effect relative rotation between the nut 40 and the shielding barrel 18 in ythe opposite direction so as to separate the two connector parts.

As alluded to hereinbefore, the connector of the present invention is not only waterproof lbut is also shielded so as to preclude radio interference. This result is accomplished by utilizing one or more coengaging grooves and indentations on the mating parts of the connector.

It will be understood that while the invention has been described specifically with reference to a preferred embodiment thereof, changes and modifications may be madeall within the `full and intended scope of the claims which follow.

We claim:

1. In a shielded spark plug assembly, an elongated insulator having a center electrode freely extending therefrom and having an upper and lower portion, a tubular shell enveloping the lower portion of the insulator and having a -ground electrode secured thereto, a shielding barrel having one end thereof connected to the shell and located coaxially with the upper end of lthe insulator, a pair of diarnetrically loca-ted bayonet grooves formed in the other end of said barrel, each of said grooves termi- -nating with a locking portion, a tubular detachable connector comprising a body portion having an annular skirt at one end thereof and a radially inwardly extending ange at the other end, a pair of diametrically located indentations formed in said skirt, a shielding sleeve having one end thereof projecting into said connector and terminating with a rst tferrule, a irst coil spring confined between the `first ferrule and the hanged end of the connector, an ignition cable having a terminal end, a tubular guide rfor said cable having an enlarged shoulder with one end thereof abutting the upper portion of the insulator, a second ferrule mounted on said shoulder, a second coil spring interposed between said rst and second ferrules, said cable terminal end adapted to be electrically con nected to the center electrode by axially moving said connector so as to engage the indent-ations with said bayonet grooves followed by a slight rotation of the connector whereby said coil springs are pl-aced in axial compression to maintain said indentations in the locking portion of the groove and said cable `guide shoulder is placed in snug engagement with the upper portion of the insulator.

2. In a shielded spark plug assembly, an elongated 4tubular insulator having a center electrode Afreely extending therefrom, said insulator having an upper and lower por tion, a tubular shell enveloping the lower portion of said insulator and having a ground electrode secured thereto and extending toward the -free end of said center electrode so as to deine a spark gap, a shielding barrel having one end thereof connected to said shell and located coaxially with the upper end of the insulator, the free end of said barrel being `formed as a thin walled section, a pair of `diarnetrically located external bayonet grooves formed in said thin walled section, each of said grooves including yan entrance portion extending in a direction longitudinal with respect to said insulator, a helical groove portion `connected with said entrance portion and terminating with a locking portion, a detachable connector comprising a body portion having an annular tubular skirt at one end thereof and a radially inwardly extending ange at the other end, a pair of diametrically located circular indentations formed in said skirt and extending internally therefrom, a shielding sleeve having one end thereof projecting into said connector and terminating with a rst ferrule, a irst coil spring confined between the first ferrule and the anged end of the connector, an .ignition cable having a terminal end, a tubular guide for said cable having an enlarged shoulder with one end thereof abutting the upper portion of said insulator, la second ferrule mounted on said shoulder, a second coil spring interposed between said tirst and second ferrules, said cable terminal end adapted to be electrically connected to said center electrode by axially moving the connector so as to engage the indentations with said bayonet grooves `followed by a slight rotation of the connector whereby said coil springs are placed in axial compression to maintain said indentations in the locking portion of the bayonet groove and 4said cable .guide shoulder is placed in snug engagement lwith the upper portion of the insulator.

References Cited in the le of this patent UNITED STATES PATENTS 2,705,308 Howard Mar. 29, 1955 2,710,386 Hall June 7, 1955 2,913,696 Burgher Nov. 17, 1959 FORETGN PATENTS 209,818 Australia Aug. 14, 1957 362,385 Great Britain Dec. 2, 1931 

